Transglutaminases are enzymes that catalyze the crosslinking of proteins by epsilon-gamma glutamyl lysine isopeptide bonds. While the primary structure of transglutaminases is not conserved, they all have the same amino acid sequence at their active sites and their activity is calcium-dependent. Transglutaminase 2 acts as a monomer, is induced by retinoic acid, and appears to be involved in apoptosis. Finally, this protein is an autoantigen implicated in celiac disease (1).